Lollapalooza 2018 runs from August 2-5 in Chicago's Grant Park, featuring headliners including The Weeknd, Bruno Mars and Jack White. Click to see more images from this year's festival. Rob Grabowski/Invision/AP

CHICAGO - It was cloudy over Lollapalooza in Grant Park Thursday afternoon — in more ways than one.

The Chicago mega-festival kicked off Thursday, with about 100,000 people once again expected each of the four days. But it took eight days, as opposed to 2½ hours last year, for full festival passes to sell out. Safety concerns may have been one of the factors: before the mass shooting at Route 91 Harvest Festival in Las Vegas last October, the gunman rented rooms overlooking Grant Park during Lollapalooza weekend, but never checked in.

Security was tighter this weekend, a necessary and welcome development. And once Thursday highlights like Travis Scott, Camila Cabello and Khalid took the stage, Lollapalooza once again fulfilled its party hard mission statement.

Travis Scott takes a trip to 'Astroworld': Three years ago rapper Travis Scott's Lollapalooza set lasted a scant five minutes, after he encouraged fans to jump the barricades and storm the stage. Not only that, he was arrested for disorderly conduct.

So it was quite the flex that Kylie Jenner's other half not only came back to Lollapalooza Thursday, but he got to headline one of the main stages — and use the festival as part of his marketing push for new album "Astroworld," which dropped on streaming services an hour after Lolla ended.

"Astroworld" tracks like the blazing "Stargazer" and bouncing "Butterfly Effect" factored into the set, but Scott (wisely) didn't opt for a front-to-back premiere party, going back to older favorites like "Mamacita." From the first second it was the most intense set of the day, with Scott bursting onto the stage with the ferocity of a bullet, but it didn't descend into true chaos this time out. Scott even stopped the set for several minutes when fans flagged him that someone had collapsed and needed medical attention, assuring the fallen fan, "I've got you, I've got you, I've got you."

Mellow Monkeys: Lollapalooza is a drastically different festival than when it started 26 years ago, and it still makes a few concessions to its alternative rock roots, evident again Thursday with Arctic Monkeys as one of the night's headliners.

Alex Turner and the band, though, were interested in looking even further back, to the sounds of '50s R&B and early Bowie, that influenced their latest album, May's "Tranquility Base Hotel & Casino." The band has dialed back the guitar spikes of its mainstream milestone "AM," and live, there was greater emphasis on Turner's buttery croon as he sang new album cuts like "The Ultracheese." Compared to the turned-up energy at Scott, this was downright pleasant, a rarity at Lollapalooza, but not exactly what most people long for at big events like these. At one point Turner even inexplicably lay down, looking like the sea of spent revelers chilling on the hill.

Lolla’s future is female: The Chicago Tribune reported that 62 percent of Lollapalooza attendees were female, a 10 percent increase from the year prior. And yet all the headliners are male - and a female act wasn’t even listed on the lineup poster until the fourth line. Which made Billie Eilish’s set so inspiring, and a wake-up call, with thousands of young women singing along to every word of every melodically chill, emotionally tumultuous song, from viral hit "Ocean Eyes;" to the self-despising "idontwannabeyouanymore;" to "Lovely," which got a surge of energy when Khalid made a surprise appearance. (Fans sang along, too, to a bit of Drake's "Hotline Bling," performed solo on a ukulele.)

Eilish is just 16, but she's already simultaneously ultra-confident and down-to-earth, and she clearly resonated on a deep level. If Lolla wants to best serve its core young female audience, the festival will be wise to book more female artists.

Camila crushes it: Ok, one more thing about this year’s Lolla lineup poster and I’ll move on. One female artist whose name was inexplicably far too low was Camila Cabello. Sure, the former Fifth Harmony singer just released her debut full-length solo album in January, but you’d struggle to think of another new artist whose had a more momentous 2018 than her.

At her Lolla set, she showed why, from her anthemic soaring vocals for set opener “Never Be The Same” to her sharp command of choreography as she danced in lock-step with her dancers for the salsa-seasoned “Inside Out” (which sashayed into Sean Paul’s “Get Busy”). It was a similar show to Cabello’s terrific Riverside Theater appearance in April, but she displayed even greater command Thursday. Those stadium shows opening for Taylor Swift have paid off this summer.

Next time she’s at Lolla, her name will be at the top of the poster, where it belongs.

Kids these days: How fitting that R&B-flavored pop singer Khalid kicked off his evening set Thursday with "8Teen." "Let's do all the stupid (expletive) that young kids do," he sang during the chorus, with thousands singing along.

A curmudgeon might put "Lollapalooza" at the top of the "stupid (expletive)" list, and they could make their case right there at that stage. In the 10 or so minutes before his set began, security pulled out at least five exhausted people from the crushing mob.

For his part Khalid, through his life-affirming anthems like "American Teen" (notice a theme?), and a special guest appearance by Normani for their collaborative like "Love Lies," showed why young kids, and kids at heart, endure the hassles of festivals.

That being said, here's some advice from an old man to you young kids: drink plenty of water, don't party too hard, know your limits. One guy literally collapsed on me as I waited for Travis Scott. Please, Lolla goers, take care of yourselves.